In the past, there has been a compression technology for compressing data, thereby reducing the size of the data. Examples of the compression technology include a reversible compression (lossless compression) technology capable of decompressing compressed data into data before compression. Examples of the reversible compression technology include compression technologies utilizing a compression algorithm called “Lempel-Ziv 77 (LZ77)” and a compression algorithm called “Lempel-Ziv-Markov chain-Algorithm (LZMA)”.
As a related technique, there is a technique that classifies records of an information file into sets each sharing common partitioned data and that sorts pieces of partitioned data, which constitute one record, by the types of partitions, thereby performing compression, for example. In addition, there is a technique that acquires log data, extracts time information, and divides the time information into information with predetermined data widths, thereby generating byte groups, wherein the technique compares values for each of anterior and posterior byte groups and calculates a difference of the values, thereby generating difference value information, and compresses the difference value information, based on the LZ77 method, for example.
Related techniques are disclosed in, for example, Japanese Laid-open Patent Publication No. 11-65902 and Japanese Laid-open Patent Publication No. 2012-235289
However, in the above-mentioned related techniques, a compression efficiency is deteriorated in some cases. For example, compared with a case where the same character string repeatedly occurs at relatively near positions in data (compression target data) to be compressed, when the same character string repeatedly occurs at relatively distant positions, the size of compressed data tends to be increased.